An EEG machine permits the recording of specific brain wave patterns in a patient. An MRI machine can provide metabolic and anatomical information regarding a portion of a patient, including a portion of the patient's brain. However, in the prior art, it has not been possible to record an EEG pattern at the same time that MRI is conducted. This prevents the obtaining of metabolic and anatomical information that is correlated to particular neurophysiological waveforms being studied. By obtaining such a correlation, it would be possible to obtain increased information regarding abnormal as well as normal brain activity and to obtain a better understanding of the functioning of the brain.
The nature of the MRI and EEG severely restrict the ability to record the EEG during magnetic resonance imaging. For example, the strong and rapidly changing radio frequency fields present during MRI, coupled with the large static magnetic field, may induce significant current flow in electrodes and wires located within the magnetic field. When conducting an EEG, the electrodes are connected to a patient's scalp, where the current may produce localized heating or burns.
Also, the equipment necessary to obtain the EEG can interfere with the diagnostic quality of the MRI images. This occurs both because the electrodes produce artifacts on the MRI images and because any radio frequency sources associated with the EEG equipment will interfere with the MRI images.
In addition, the radio frequency and magnetic fields can compromise the quality of the EEG or even make it impossible to obtain.
Currently, patients receiving an MRI who also are having their EEG recorded generally will have the EEG electrodes removed before there are placed in the MRI machine. In some cases, the electrodes are left in place during an MRI, but those electrodes have caused artifacts on the MRI image and it has not been possible to record the EEG during the MRI process.
It is therefore an object of the present invention to provide a method and apparatus for obtaining an EEG during magnetic resonance imaging.
It is another object of the present invention to provide a method and apparatus for triggering an MRI image in response to specific EEG signal patterns.